Adjustable condenser



R. M. KLEIN ADJUSTABLE c oNDENsER sept. 6, y1927'. l

Filed NOV. l, 1924 BY PM, 5w/Wm may ATTOD NEY5 Ficha@ M /f/@fh -mimmF-gmr Patented Sept. 6, 1927.

RICHARD M. KLEIN, OF NEW YORK, N. Y., SSIGNR T0 F. A. D. ANIGREA,Xiti-C., F YORK, N. Y., A CORPORATION 0F NEW YGRK. l

ADJUSTABLE CONDENSER.

Application led November This invention relates in general to electricsystems or circuit arrangements of were signaling systems such cs thosedescribed in U. S. Letters Patent to Hitzeltine Nos'. 1,450,080 und1,489,228, wherein inherent or natural capacity coupling between pnrtsor portions thereoic is' neutralized by the proper adjustment ot' ucondenser of extremely I small capacity; and has for its object theprovision of e condenser of improved de sign particularly applicable toneutralizing undesirable capacity coupling in radio receivers utilizingvarious types of vacuum tubes ot diiiierentcharacteristics.

'in order to change vacuum tubes ot one type to vacuum tubes -ot anothertype in indio receiving apparatus which employs neutralization otcapacity coupling, it has heretofore been neccessary to repent thepermanent adjustment of the neutralizing condensers by ineens of thesomewhatcninber sonic balancing process required at the time when thereceiver is first assembled.

The present invention provides e neutrnlizing condenser which may bepermencntly adjusted initially to elect the neutnlizution ot thcinherent inter-electrode capacity of various types of tubes, any one otwhich only thereafter be used in the saine receiver with the mererequirement of setting tlieneutralizing condenser to the permanentposition indicated thereon ns beingl the proper settingpredetermined forn given type oi tube.

A better understanding.;- ot the present invention und :in additionalappreciation of its advantages may' be had from e consideration of thefollowing,T description of n preferred cnibodin'ient us illustrated inthe uccoinpunying' drawings, in which I Fig.' l represents n plan viewof nn ndjustsblc condenser incorporating this invention; i Fig. '2 is everticalv section taken through line 2-`2 ot' Fig. l; and l Fig. l shows:rcircuit diagram of n cepncity-neutrnlized -tuned odio-frequency:unplitier to which this invention .is especially applicable.

Reterring new to Figs. l and 9. of the drawing: The adjustable condenseris mounted upon nu insulating bese 1 and mcy comprise utubular metallicelectrode 2 snrroundingv n tubulnr dielectric il, which may be oi :mysuitable dielectric nintcrinl such i, 1924. Serialy No. 'M'il ns or hardrubber, and one, or pret# erebly tirol-inside rod-like electrodes Ilsind lt will be observed that the electrode i is not ,fixed as iselecLrode 5, but .it is inov` able and nniy he adjusted axially withreifcrcnce to electrode i). in order to very the dielectric sur'ieceincluded between electrodes t2 and f-i. As represented in the dren ing,electrode 5 is preferably stationery and is secured by e screw toconnecting lng; Electrodes -i und 5 are conveiiiently formeel from No.'le B. & S. gauge copper Wires,v

electrode i being longer and having e nie nipuleting handle Z on itsoutside end. This handle is so orined 'es to serve es en indicntorS,which niny be set et any desired indicated position 9, such os E or Simarked on base 1. The letter D in this instance represents e, setting orthe condenser ivhich will serve to neutralize the inherentinterelectrode capacity coupling ot n so celled dry cell. tube inaccordance with the disclosure ot the aforementioned. Einzel patents;and, likewise, the letter Si represents the proper .setting neutrniize.the inherent nter-electrode capacity conpling of e fao-celled storagebattery tribe. it the capacity of the neutrali.' g condenser vis sochosen relatively to the number or turns Nl' and N2 of coils L1 and L25Fig. Si, respectively, that the ratio of the inter electrode capacity tobe neutralized to the capacity oi the neutrulizii'ig Acondenser is aquelto vlthen the ningneto-motive force ot' Lfc will equal end cancel thatof LU provided the coils have the proper relative polin-ity, viz, theterminals connected together niust be of unlike polarity. No voltagewill then be induced in either coil, and, therefore, no variation canoccur in the grid potentiel due to the variation in the plete potenQtial, assuming the resistnnces of' the coils negligible in comparison totheir reoctences;

Elli

hence the undesirnble etl'ects ott espec-ity 300 coupling will have beeneliminated. A vltnll and complete discussion of this method forneutralizing capacity coupling Wiil be found in the Hiizeltine ,patentsreferred to. lt is,

or course, sometimes desirable to mori: these W5 positions in otherWays, such es by indi eating the vaines et the cnpeciti s directly, orby using on arbitrary scale. Fig. I, illnstretiiig the preferredeniliodiinent, shows the indications inerlred upon the lease of thecondenser, but it is frequently convenient to place marks upon thecondenser itself, particularly when space does not permit of a scale orother indicating means. In order that any desired adjustment of thecondenser may be maintained and an accurate setting held indefinitely,notches 10 have been provided inl electrode 4, into which engagespro]ection ll of a spring Contact member` l2. A screw having a slottedhead 13 may be provided to support the electrode l under the pressure ofspring l2 so that the electrode may slide longitudinally through theslot. Spring 12 is secured to the base l by a screw f2() and terminatesin a connecting lug 14,10 which a connecting wire may be attached.Ordinarily the condenser is con'- nected into its circuit by means oflugs G and 14;, this connection resulting actually in two capacitiesbeing connected in series, the first oapacityexisting between electrodes5 and 2, and the second capacity between electrodes 2 and Il, Theresultantcapacity of these two in series may, be varied by n g Aslidingintermediate electrode 2 so as to 1nclude more or less dielectricsurface between it and the two inside electrodesy and also, asabovedescribed, by sliding electrode et infer out of the dielectric tube 3.lt is preferable, practically, to set the intermediate lelectrode 2 atthe time when the lcondenser is first calibrated and `then to lool; thatelec- -trode againstr inadvertent movement by means of clamp 17 andscrew lo. Lug 1F "is provided to make contact with electrode 2 in casethe connection through lug t provides too small a resultant capacity.The dielectric tube 3 is secured against movement by means of a clamp 19and screw 18,.

At the present time there are on the American market `vacuum tubes, vforreception purposes, of three general types ranging in grid-platecapacities from about 15 micronfiicrofarads to about 25micro-microfai-ads. Two'of these types are adapted to be supplied withfilament heating current derived from dry cells, and the other type isadapted to Idraw current from storage batteries. lt is thus possible forthe owner of a receiver incorporating the-invention described herein tochange from dry cell tubes to storage battery tubes with the solorequirement of moving the setting of the neutralizing condensers fromposition D .to S with the assurance that the receiver will then becorrectly neutralized. Since the initial cali-bration and permanentsetting of the neutraliz- `ing condensers for the proper and ellicientoperation of radio receivers embodying the Hazeltine principle ofneutralization of capacity coupling involves the use of an elaboratetesting apparatus and skill not to be expected of the general public, itwill lbe readily appreciated that the present invention provides anextremely simple means for making feasible the interchange of vacuumtubes of certain definite characteristics in the type of receiver towhich this invention is peculiarly adapted.

The wiring diagram of such a receiver is shown in Fig. 3, whichrepresents a radio receiver embodying two stages of timed radiofrequencyamplification in which the gridplate coupling capacity of the vacuumtubes A and A1 is neutralized by neutralizing condensers (l, and Cu incooperation with a winding' of interstage coupling transformers T1 andT2 respectively. A detector tube A: is shown lconnected in thecuston'iary manner to the output of transformer TQ, and includes in itsplate circuit telephone receivers R. In order to simplify the diagram,the usual audio frequency amplifiers have been omitted from Fig. 3,since it is here desired to illustrate the application of this inventionto a radio-frequency amplifying system. rl`he present invention isobviously applicable to other uses, however, such as the neutralizationof capacity coupling between coils, lietween portions of variouscircuits, or between electrodes of vacuum tubes utilized for variousother purposes.

I claim:

An electrostatic condenser comprising` two rod-like electrodes. one ofsaid electrodes being movable toward and away from the other forvarying` the capacity of the condenser. said movable electrode beingprovided with a pluralit)r ol" spaced .stops and means oper-- able toengage said stops individually` said means and said stops being operableconjointly to maintain. the selling of the condenser at any one of aplurality of predetermined capacity falues.

In testimony whereof lY aliix my signature.

l? llOHA RD M. KLEIN.

